MNT: define macros supplied in py39 and above
MNT: define macros supplied in py39 and above

To support the change to Py_SIZE and Py_TYPE the Py_SET_SIZE and
Py_SET_TYPE macros are provided in py39.  This provides the same
macros falling back to the old method for < py39.

mhvk/numpy,charris/numpy,endolith/numpy,jakirkham/numpy,numpy/numpy,abalkin/numpy,pbrod/numpy,numpy/numpy,pbrod/numpy,mhvk/numpy,mattip/numpy,pdebuyl/numpy,charris/numpy,madphysicist/numpy,mattip/numpy,pdebuyl/numpy,charris/numpy,mattip/numpy,seberg/numpy,grlee77/numpy,madphysicist/numpy,endolith/numpy,mhvk/numpy,rgommers/numpy,jakirkham/numpy,madphysicist/numpy,abalkin/numpy,abalkin/numpy,mhvk/numpy,jakirkham/numpy,grlee77/numpy,grlee77/numpy,seberg/numpy,grlee77/numpy,mattip/numpy,numpy/numpy,anntzer/numpy,jakirkham/numpy,pdebuyl/numpy,anntzer/numpy,madphysicist/numpy,charris/numpy,seberg/numpy,seberg/numpy,simongibbons/numpy,jakirkham/numpy,simongibbons/numpy,pdebuyl/numpy,rgommers/numpy,simongibbons/numpy,grlee77/numpy,endolith/numpy,endolith/numpy,rgommers/numpy,anntzer/numpy,anntzer/numpy,rgommers/numpy,simongibbons/numpy,simongibbons/numpy,numpy/numpy,pbrod/numpy,pbrod/numpy,madphysicist/numpy,pbrod/numpy,mhvk/numpy